Communication devices such as terminals are also known as e.g. User Equipments (UE), mobile terminals, wireless terminals and/or mobile stations. Terminals are enabled to communicate wirelessly in a cellular communications network or wireless communication system, sometimes also referred to as a cellular radio system or cellular networks. The communication may be performed e.g. between two terminals, between a terminal and a regular telephone and/or between a terminal and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network.
Terminals may further be referred to as mobile telephones, cellular telephones, laptops, or surf plates with wireless capability, just to mention some further examples. The terminals in the present context may be, for example, portable, pocket-storable, handheld, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server.
The cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the terminals within range of the base stations. In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to the mobile station. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the mobile station to the base station.
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks.
UMTS is a third generation mobile communication system, which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for terminals. The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies.
3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE controlled by the radio base station.
A number of peer-to-peer technologies are used to connect devices wirelessly, such as WLAN or Bluetooth. To enable neighboring devices within wireless range to discover each other, these technologies employ a device discovery procedure whereby one of the devices sends beacon signals, which is received by the other device, and hence it becomes aware of the sender's vicinity.
Recently, a technology has been proposed to enable a kind of “wireless sense” where all devices equipped with this technology can discover each other. This technology, similarly to Bluetooth, does not require or make use of a network infrastructure, other than that this technology utilizes signals for node synchronization.
Cellular network assisted Device-to-Device (D2D) communication has recently been proposed as a means of increasing the spectrum efficiency, reducing the resource usage and minimizing latency for short range communications. Similarly to the wireless sense technology and Bluetooth, peer discovery is a prerequisite for network assisted D2D communications as well, that enables devices to detect that they are in the proximity of one another.
D2D communication enables a direct link of a device, user equipment UE, terminal, etc to another device. This provides large volumes of media or other data to be transferred from one device to another over short distances and using a direct connection. This form of device to device transfer would enable the data to be transferred without the need to run it via the cellular network itself, thereby avoiding problems with overloading the network and enabling proximity based applications such as to enable new types of applications that rely on proximity awareness.
Regarding wireless peer-to-peer technologies such as WLAN or Bluetooth, the discovery process comprising transmitting, receiving and processing beacon signals consumes energy in both the transmitter and the receiver devices. Further they use scarce wireless resources e.g. spectrum and power. The existing peer discovery technologies operate independently of the underlying cellular network. Typically, the device discovery phase of Wireless Local Area Network (WLAN) or Bluetooth is triggered by a user of a device. For this reason, the discovery process is limited in time, frequency and power, and performed only when needed.